a) Field of the Invention
This invention relates to temperature-controlled appliances useful at home or the like and having combined functions such as freezing, cold storage (refrigeration), defrosting and warm storage of foods and the like, and especially to temperature-controlled appliances making use of Peltier devices.
b) Description of the Related Art
(First related art)
In a general household refrigerator of the compressor type, a freezer compartment and a refrigerator compartment are located at specific places. Their capacities are fixed, namely, unchangeable, and their temperatures cannot be set to any values outside corresponding predetermined ranges. Defrosting of a frozen food has been conducted at a place different from the refrigerator, for example, in a microwave oven.
(Second related art)
Keeping in step with the availability of longer leisure time in recent years, there is an increasing tendency toward enjoying outdoor activities, parties and the like. This has led to increasing developments of portable coolers. FIGS. 36 and 37 illustrate such conventional portable coolers.
In the portable cooler of FIG. 36, a metallic container 1102 made, for example, of aluminum is arranged inside a heat-insulating container 1101, and a peltier device 1105 is disposed in a side wall 1103 of the metallic container 1102 at substantially a middle position with a heat-absorbing-side thermal conductor 104 interposed between the Peltier device 1105 and the side wall 1103.
A heat-dissipating-side fins 1106 are arranged in contact with an outer side of the Peltier device 1105. A heat-dissipating fan 1107 is arranged in a close proximity of the fins 1106. An opening of the heat-insulating container 1101, said opening is located at a top of the heat-insulting container, is closed by a heat-insulating cover 1108.
Transfer of heat in the portable cooler takes place in the order of the metallic container 1102.fwdarw.the heat-absorbing-side thermal conductor 1104.fwdarw.the Peltier device 1105.fwdarw.the heat-dissipating-side fins 1106. The heat-dissipating-side fins 1106 are cooled by air from the fan 1107.
In the portable cooler of FIG. 37, a heat-insulating cover 1108 is provided with a heat-absorbing-side thermal conductor 1109, a heat-absorbing-side thermal conductor 1104, a Peltier device 1105, heat-dissipating-side fins 1106 and the like. A heat-absorbing-side fan 1110 is arranged inside a heat-insulating container 1101. In this case, a material placed for being chilled within the heat-insulating container 1101 is indirectly chilled by a stream of air produced by the heat-absorbing-side fan 1110.
(Third related art)
Frozen foods include frozen seafoods, meat (including poultry and game), vegetables and processed frozen foods. For defrosting these foods, there are a variety of methods, for example, air defrosting methods such as stationary air defrosting, humidified-air blast defrosting and compressed-air blast defrosting; water defrosting methods such as water-dipping defrosting, spray defrosting and steam defrosting; contact defrosting methods such as contact defrosting and aluminum contact defrosting; and electric defrosting methods such as electric resistance defrosting, dielectric heating defrosting (high-frequency defrosting and microwave defrosting), far infrared defrosting, and electrostatic defrosting. For each of these defrosting methods, various proposals have been made.
Concerning freezing of foods and the like, it has been the conventional practice, except for certain special cases, to place a desired food, for example, meat, fish, a vegetable or the like in a freezer compartment of a refrigerator and to freeze it by spending a lot of time.
(First problems)
In the refrigerator according to the first related art, the capacities of the freezer compartment and refrigerator compartment have been specified beforehand. If frozen foods are bought in a large quantity, the frozen foods cannot be stored in their entirety in the freezer compartment so that some of them have to be stored in the refrigerator compartment. Therefore the frozen foods placed in the refrigerator compartment are defrosted and can no longer remain in the frozen state.
In freezing, a food which is desired to be frozen ad has a high temperature is placed in a freezer compartment in which frozen foods have already been stored. This causes temperatures of the foods, which have been stored in a frozen state, rise locally, thereby possibly deteriorating the quality of the foods.
Further, the capacities of a freezer compartment and a microwave oven are fixed in the conventional art. Accordingly they cannot freeze or defrost a great deal of foods at once, leading to the inconvenience that long time is needed for freezing and defrosting.
(Second problems)
The portable cooler of the indirect cooling system, which is shown in FIG. 36 and pertains to the second related art, is poor in cooling efficiency. Moreover, the heat-insulating cover 108 is heavy because of the arrangement of the heat-absorbing-side thermal conductor 1109, the heat-absorbing-side thermal conductor 1104, the Peltier device 1105, the heat-dissipating-side fins 1106 and the like. In addition, it is necessary to arrange the heat-dissipating fan 1107 near the heat-dissipating-side fin 1106. Furthermore, the heat-insulating cover 1108 is provided on the inner side thereof with the heat-absorbing-side thermal conductor 1109, leading to drawbacks such that certain limitations are imposed on open/close operation of the heat-insulating cover 1108 and the portable cooler itself does not have much design tolerance.
The portable cooler shown in FIG. 37 is also from the drawback that efficent cooling cannot be obtained from the consumed electric power. The present inventors have studied this matter in various ways. As a result, it has been found that the poor cooling effects can be attributed to the arranged position of the Peltier device 1105 and the position of the upper edge of the metallic container 1102.
This will be described specifically. In the conventional portable cooler, the Peltier device 1105 is arranged in only one (i.e., the side wall 1103) of the side walls of the metallic container 1102 and moreover, at substantially the middle position of the height. There is hence a long creeping distance especially between the side wall 1103, in which the Peltier device is arranged, and the side wall 1103 located opposite the former side wall 1103, so that the temperature distribution within the portable cooler tends to become uneven.
Further, the upper edge of the metallic container 1102 extends to the opening of the heat-insulating container 1101 and moreover, the Peltier device 1105 is located near the upper edge. Whenever the heat-insulating cover 1108 is opened, the temperature of the top edge of the metallic container 1102 immediately rises. Even while the heat-insulating cover 108 is kept closed, there is still transfer of heat from between the heat-insulating container 1101 and the heat-insulating cover 1108. As a consequence, the cooling effects are reduced by these heat.
(Third problems)
In connection with the third related art, the quality of a food before defrosting, the defrosting speed, the defrost completion temperature and the defrosting method can be mentioned as elements which determine the quality of the food after defrosting. In freezing, the freezing speed gives more influence to the quality of a food than the freezing completion temperature. In defrosting, however, the defrost completion temperature gives greater influence to the quality of a good than the defrosting speed, because a deterioration in quality after defrosting proceeds in proportion to a rise in temperature and may proceed faster than fresh foods.
The conventional defrosting methods involve the drawback that, because the temperature of a defrosted food gradually rises due to the surrounding temperature when the food is left over subsequent to its defrosting, it is impossible to set a defrost completion temperature suited for the food or to retain the defrost completion temperature and the quality of the food is substantially deteriorated by defrosting.
Further, a conventional, especially household freezer freezes a food under fixed conditions without distinguishing, for example, an animal food and a vegetable food from each other. This often leads to broken cells and tissues of foods or to improper frozen state, so that the quality is reduced when defrosted.
In freezing, a food which is desired to be frozen ad has a high temperature is placed in a freezer compartment in which frozen foods have already been stored. This causes temperatures of the foods, which have been stored in a frozen state, rise locally, thereby possibly deteriorating the quality of the foods.